The present invention relates to a rotation mechanism and a producing method thereof, and more particularly, to a welding structure and a welding method of a rotation shaft and a fixed member.
Conventionally, as one example of the rotation mechanism and its producing method, Jpn. Pat. Appln. KOKOKU Publication No. 2-1498 discloses a technique concerning an endoscope nipper device.
This endoscope nipper device will be explained using FIGS. 7 and 8.
In FIG. 7, a connection piece 124 of a pair of nippers 119 is connected to a tip end 126a of a nipper operating wire 126 inserted through a flexible tube 121 through links 125 and a wire joint hardware 127.
A rear end (not shown) of the nipper operating wire 126 is connected to a nipper operating device (not shown) of a nipper operating portion.
By moving the nipper operating device backward and forward, the nipper operating wire 126 can be advanced and retreated in the flexible tube 121.
With the advancing and retreating movements of the nipper operating wire 126, the wire joint hardware 127 advances and retreats, so that the pair of nippers 119 can open and close around a pivot pin 130 fixed to a slotted opening cover 129 of a nipper head 123.
The pair of nippers 119 of the endoscope nipper device of the above structure have connection pieces 124 projected from connected portions 119a of both the nippers 119 are connected to links 125 through connection pins 131, the links 125 are connected to the operating wire 126 through the wire joint hardware 127, the connected portions 119a of both the nippers 119 pivot for opening and closing movements at the slotted opening cover 129 of the nipper head 123.
In the endoscope nipper device of the above structure, a connecting method, using laser welding, of the connection pieces 124 of the nippers 119, the links 125 and the connection pins 131 will be explained by using FIG. 8.
First, the links 125 abut against connected portions 124a of the connection pieces 124, connection holes 124b of the connection pieces 124 and connection holes 125a of the links 125 are aligned with each other, and connection pins 131 are inserted to the connection holes 124b and 125a.
Here, the length of each of the connection pins 131 is set to a value which does not exceed the sum L1 of a plate thickness of the connection piece 124 and a plate thickness of the link 125.
Flat heads 131a of the connection pins 131 are flush with a side of the links 125.
Further, weld ends 131b of the connection pins 131 are flush with a side of the connection pieces 124.
In this state, the weld ends 131b of the connection pins 131 are radiated with a laser light, and the weld portions 131b are welded along opening edges of the connection holes 124b of the connection pieces 124.
However, the above-described prior art has the following problems.
That is, when the connection pins 131 are inserted to the connection holes 124b and 125a, it is necessary to precisely position the three parts, i.e., the connection piece 124, the link 125 and the connection pin 131.
If the number of parts which need to be positioned is great, a control apparatus for an automatic welder is increased in size, which increases the costs.
Further, there are problems that the time required for the welding becomes long, and the efficiency of the automatic welder is lowered.